High speed press control



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May 19, 1942.

May 19, 1942. w, E NST EIAL HIGH: SPEED PRESS CONTROL Filed Sept. 19,1940 6 sheets sheet 4 Q up wk M u 4 9 MR2: l 2 m 2 t O 9 E y F 2 I .5 67 m M g 5 w. m I 7 7 W MM w. 2 M 6 M9 5 5 I /J-= I all m m I. ,0 1 a m mw 5 H w- M 6 IM 7 w m .5 w W 2 I May 19, 1942. w. ERNST ETAL ,2 HIGHSPEED PRESS CONTROL 7 v Filed Sept. 19, 1940, I 6 Sheets Sheet5 Ell]4TTOR/IEYS May 19, 1942 w. ERNST EI'AL v 7 2,283,168v

HIGH SPEED PRESS CONTROL Filed Sept. 19, 1940 ,6 Sheets-Sheet 6 .EElE

Mama's mu rm mm mum 111mm? Mal- . Patented May 19, 1942 UNITED STAT B8TENT orFlci:

I HIGH SPEED PRESS CONTROL Walter Ernst and Philip .1. Lindner, MountGilead,

Ohio, assignors to The Hydraulic Development Corp., Inc., Wilmington,Del., a corporation of Delaware 1 Application September 19, 1940, SerialNo. 357,444

22 Claims.

This invention relates to hydraulic presses, and in particular tohydraulicv presses in which provision is made for slowing down themovement of the press platen shortly before the work piece is engagedby-the die connected with said platen. Devices of this type,-asheretofore known, have the drawback that if for some reason it has beenomitted to insert a work piece in the press so that no resistance isencountered by the press platen, the press will immediately speed upagain to full speed. This may result in injuries to the operator andalso completely ruin the. die.

Accordingly it is an object of the invention to position, while electricmeans for shifting said reversible variable delivery pump is arranged soas to shift the pump to full delivery forward and retraction strokerespectively at the beginning and end of the working stroke, and toshift the pump into restricted position shortly before the point whereit normally engages the work piece,

provide a press of the above type in which the:

press platen after being slowed down, prior to reaching its work pieceengaging position, will not be speeded up when-it has been omitted toinsert a work piece.

It is another object of the invention to provide a hydraulicp'ress'comprising a variable delivery pump for delivering pressure fluid to thepress platen, in which the pumping stroke is reewhen, due to theengagement of the press platen with the work piece, a predeterminedpressure builds up in the press cylinder.

It is another object of the invention to provide a hydraulic press inwhich the press cylinder is supplied with pressure fluid from a. onewayvariable delivery pump normally urged to a restricteddelivery positionbut adapted by electric means to be shifted to full stroke deliveryposition, and inwhich said pump is-allowed to return to its restricteddelivery position shortly before its work piece engaging position isreached and toremain in said restricted delivery position untilapredetermined pressure in the press cylinder causes a change in theenergization ofthe circuit comprising said electric means.

It-is still another object of the invention to provide a hydraulic pressin which the press cylversible variable delivery pump with centeringsprings constantly urging-the pump to neutral in which restrictedposition it is maintained during the rest of the advancing stroke of theplaten unless a predetermined pressure develops and acts on said pressplaten.

A still further object of the invention consists in the provision of ahydraulic press with a reversible variable delivery .pump for supplyingpressure fluid to the press cylinder, in which an electricallycontrolled and air pressure operated system automatically restricts thesupply of pressure fluid from said pump to the press cylinder when thepress platen approaches the-point of travel at which the work piece isnormally engaged, and in which the pump is restored to full delivery.position when, due to the engagement of the work piece, a predeterminedminimum pressure builds up in the press cylinder.

It is another object of the invention to provide a hydraulic press ofthe character set forth in the preceding paragraph, in which twovariable delivery pumps are simultaneously operated by an electriccontrol and air pressure system.

Theseand other objects and advantages of the invention will appear moreclearly from the following specification in connection with theaccompanying drawings. in which; V

Figure 1 diagrammatically" illustrates a' press assembly according to afirstembodiment of the invention. I

Figure 2 shows; on .-a somewhat larger scale, the upper portion ofFigure land is supposed to be a section along the -line22 of Figure 8.

Figure 3 is a section along'the line, 3-3

- ofFigure 8.

inder is supplied with -'pressure fluid from a re-' Figure 2.

Figures4, 5 and 6 aresections similar to that of Figure 3 and show apart of the linkage system. in various positions. I

Figure 7 shows a section of the air cylinder used in connection with thelinkage shown in Figure 8 is a top view section.

.Figure 9 illustrates the electric diagram for I the first embodimentof'th'e invention shown in Figures 1 to 8.

Figure 10 is a second embodiment of. the in- ,vention inwhich thelinkagesystem with the air cylinder of the first-embodimentof the invnof Figure 2 partly I GENERAL ARRANGEMENT The press according to thepresent invention is supplied with pressure fluid by a variable deliverypump which, when the press platen approaches a position in which thework piece is normally engaged, is shifted so as to materially reduceits delivery, thereby slowing down the movement of the press platen. Thepressure now prevailing in the press cylinder is conveyed to a lowpressure responsive valve which is so adjusted as to be actuated onlywhen a minimum pressure builds up in the press cylinder due to theengagement of the die carried by the press platen with the work piece.Unless this minimum pressure is obtained, the variable delivery pumpremains in its restricted delivery position. However, when the saidminimum pressure is built up, actuation of the low pressure responsivevalve causes a change in the energization of an electric circuitcomprising means for effecting a shifting movement of the pressure pumpto full forward delivery position, thereby enabling the press platen tocarry out its working stroke.

According to the first embodiment of the invention shown in Figures 1 to9, air pressure is conveyed to the smaller area of a double-acting airpiston so as. to put the variable delivery pump on full stroke forwardposition. When approaching its work piece engaging position, the press,platen engagesv a switch which. closes an electric circuit controllingthe operation of an air valve which admits-compressed air to the largerpiston area of the said air piston operatively connected with the flowcontrol member of the variable delivery pump. The operation of said .airvalve and admission of compressed air to the larger piston area of saidair piston causes a restriction of ,the variable delivery pump, therebyslowing down the movement of the press platen. The pump remains in thisrestricted position unless the press platen engages a work .piece sothata minimum pressure builds up in the cylinder which actuates the lowpressure responsive valve in such a manner as to de-energize the circuitcomprising the switch so that the air pressure acting on the smallerpiston area of the air-piston restores the pump to full deliveryposition. The press platen then, continues its workingstroke in theusual manner.

According to the second embodiment of the invention the air piston ofthe first embodiment and the linkage connected thereto is replaced by areversible variable delivery pump with 'cen- 'tering springs tending tohold the pump in neutral or no delivery position. The flow controlmember of the reversible variable delivery pump is associated with twosolenoids, oneof which when energized places the pump in full strokeforward position, whereas the energization of the other solenoid causesthe pump to. move into \f-lll stroke retraction position. The p p isfurthermore associated with 9. preferably electrically controlled stopmechanism which prevents the pump from returning fully to neutral or nodelivery position during the advancing stroke of the press platen.According to the second embodiment, the initiation of the advancingstroke of the press platen is effected by energizing the solenoidandplacing the pump into full strokeforward position. As soon as the pressplaten approaches its work piece engaging position, an electric switchis actuated which causes de-energization of the solenoid for fullstroke" forward position so that the centering springs tend to move thepump to neutral position. However, the above mentioned stop acts as alatch stopping the flow control member of the pump so that a slowdelivery of the pump is maintained, thereby enabling the press platenslowly to advance until due to the engagement of the die, carried by thepress platen, with the work piece, a predetermined pressure builds upactuating a low pressure responsive valve. Actuation oi the said lowpressure responsive valve causes re-energization of the solenoid so thatthe pump is again shifted tofull stroke. The

. press platen may then effect its pressing operation in the usualmanner.

According to the third embodiment of the invention, the reversiblevariable delivery pump of the second embodiment is replaced by a one-wayvariable delivery pump in connection with a fourway valve. In thisembodiment the variable delivery pump is continuously urged by means ora spring into a restricted delivery position, while a solenoid whenenergized shifts the pump against the thrust of said spring to fulldelivery position. The direction of flow of fluid from the pump to thecylinder is controlled by: the above mentioned four-way valve. Thedevice of the third embodiment operates similar to that of the secondembodiment. To start'a work stroke of the press platen, the solenoidassociated with the variable delivery pump is energized, thereby placingthe pump on full stroke delivery, while the fourway valve is so adjustedas to direct the fluid delivered by the pump to the advancing area ofthe press piston. As soon as the platen approaches. the work pieceengaging position,-a switch is actuated which causes de-energization ofthe solenoid so that the spring associated with the pump shifts the pumpto restricted delivery position, thereby slowing down the movement ofthe press piston. If due to the engagement of a work piece with the diecarried by the press platen a. minimum pressure builds up in the presscylinder, a low pressure responsive valve is actuated so as to restorethe energization of the solenoid thereby again placing the pump on fullstroke delivery position so that the press platen ma efiect its pressingoperation.

Srauorunsr. ARRANGEMENT reversiblevariable delivery pumps 18 and I9 re-'spectiveiy communicates by conduits 20 and 2| with the lower'portion oithe press cylinder l3.

Connected with the conduit I6 is a low pressure responsive or tonnagecontrol valve 22 adapted to communicate with the fluid reservoir orsurge tank 23 arranged on top of the press cylinder;

bore I3 and adapted to supply pressure fluid to the upper portion of thecylinder bore 13 by means of a surge valve 24. The surge valve 24 on onehand by the cylinder head 54 and on the other hand by the bottom portion58 of the cylinder bore 53. Th piston 5| carrying piston rings 59 isprovided with L-shaped bores 60 adapted to allow fluid entrapped betweenthe pistons 5| and 52 to escape into the left portion is adapted tocommunicate through a conduit Serial No. 286,063 filed July 24, 1939,likewise t0 Ernst. The purpose of the surge valve 24 merely consists inprefllling the upper portion of the cylinder bore l3 when the presspiston is moving downwardly by gravity, whereas the main cylinder reliefand pump by-pass valve 21a facilitates the reversal of the movement ofthe press platen at the end of its working stroke.

Also communicating with theconduit I6 by means of a conduit 28 is a highpressure tonnage control valve 29 which, when actuated, effects thereversal of the movement of the press platen so as to cause the latterto effect its retraction stroke.

The pressing platen I5 comprises a control spring 308 which continuouslyurges the piston to its lowermost position and is adapted to counteractair pressure acting through the con duit 36 upon the lower surface ofthe piston".

The conduit 36 also communicates with a conduit 38leading to a controlvalve, generally designated 39. The control valve 39 comprises acylinder 40 having reciprocably mounted therein a piston 4| the movementof which iscontrolled by a solenoid'42. Also in the cylinder 48 isprovided a spring 301 similar to the spring 308 which continuously urgesthe piston 4| to its lowermost position and is-adapted to counteract airpressure acting upon the lower surface of the piston 4|. Each of thecylinders 34 and 48 has,

at its uppermost end, a bleeder "opening 48 and 44 respectively. Thecylinder 34 furthermore.

communicates through a conduit 45 with the port46 at one end of an aircylinder, generally designated", while the other end of said cylindercomprises a, port 48 communicating through a check valve 49a and aconduit 49 with the cylinder 40 of the controlvalve 39 (see Figure '7).The air cylinder 41 comprises a cylinderbore. 50 having recip'rocablymounted therein a piston 5| which is adapted to moveindependently of butto engage a piston 52 reciprocably mounted in a bore 53of largerdiameter than the bore 60.- The s end adjacent the piston -52is'closed-b y a cylinder head 54 engaging a gasket 55 and connected tothe cylinder 41 by'screws 58 or any other con-' venient means. Thepiston 52 carries piston rings 51 and is U-shaped and adapted to engagea correspondingly shaped portion of the piston 5|. l'he movement of thepiston 52 is limited of the cylinder bore 53 which communicates with ableeder opening 6|. The piston 5| has threadedly 'connected therewith ashaft 62 passingthrough the other end of the cylinder 50. To

prevent leakage between the cylinder bore 50 and. the shaft-62, apacking 63 compressed by a'nut 64 is provided. The end of thecylinderbore 50 adjacent the port 48 is provided with an exhaust bore480 which is spaceda short distance from the extreme end of the bore 50so that the piston 5| covers the exhaust bore 48a before the piston 5|can engage the bottom portion 61 of the cylinder bore 50. To preventfluid from being completely entrapped between the cylinder bottom 61 andthe piston 5| when the latter in its movement toward the left (withrespect to Figures 1 and-7) has just closed the bore 48a, choke bores65, 66 are provided which are plugged toward the outside but communicatewith each other and with the exhaust bore 48a which in its turncommunicates through conduit'48b with the conduit '49. In thisway, thefluid entrapped between the cylinder bottom 61 and piston 5|, when thelatter has covered the exhaust bore 48a, can escape into the conduit 48bonly through the choke bores 66, thereby cushioning and slowing downthelast portion of the movement of piston 5| toward the cylinder bottom 61.A,

direct escape of said entrapped fluid through the bore 48 into theconduit '49 is prevented by the check valve 49a which opens only towardthe opening 48. and is arranged between. the latter and the point wherethe conduit 48b leads into the conduit 49. Threadedly connected with theshaft 62 and secured by a nut 68 is ayoke 69 connected by means ofa'link I0 with an arm II keyed to the shaft I2 by means of a key I3 (seeFigure 8). Likewise keyed to the shaft I2 by means of a key I4 is an armI5 pivotally connected with a'rod'16 by means of. a yoke I1 and pistonI8. The rod I6 is pivotally connected by means of-a yoke I9 and pivot'with an arm 81.

The arm 8| is mounted upon a pivot pin 82 sup-- ported by a link 83pivotally mounted upon a. pin 84 supported by the lug 85 upon theservomov tor cylinder head 86. Connected with the flow control member(not shown) of the pump is a shift rod 81 pivotally connected by meansof a yoke ,88 and pin 89 with the lowermost portion of the arm 8|. Thshift rod 81 has mounted thereon an abutment 90 (Figure 1) engaged by aspring 9| urging the shift rod 81 toward the 1 outside so as to put thepump on full stroke delivery position. Rigidly connected to the shaft I2by keys 92 .and 93 (Figure 8) is the. arm 94 composed of 'two members 95and 96 having a sleeve 91 therethrough on which is hinged the link 98pivotally connected by a pivot 99 with the arm I00 which; similar to thearm 8| is connected by a link II with the servomotor cylinder head I02of the pump l8. The arm I 00 furthermore pivotally connected by'a pivotI03- and yoke I04 with the shift rod I05 pertaining to the flow controlmember of the pump I8. The

shift rod I05 likewise has an abutment 90a en'- ased by a spring 9|a.The springs 9| and 9Ia tend to actuate the push rods 81 and I05respectively. so as-to move the pumps I9 and I8 to full strokeretraction position. 1

The arm 15 has connected therewith a clutch member I06 having a singlejaw I91 engaged I by a clutch member 998 connected with the arm I09which arm is shiftable about the shaft 12.

The clutch inember I 04 has likewise a single jaw IIO cooperating withthe jaw I01. The arm I09 has at its free ends-thereof a rounded portionI II engaging a collar II2 provided at the uppermost portion of the pushrod H3. The push rod II3 has adjustably mounted thereon a collar II4engaging with its upper portion one end of a spring I I5 the other endof which abuts an arm II6 fixed to the press head I2. The spring II5urges the push rod II3 downwardly: Also adjustably mounted on the pushrod H3 is a collar nected with the terminal I55. Cooperating with theterminal I55 is. a terminal I56 connected by lines I51 and I68 with theline I29 leading to the low voltage main line I30. Cooperating with theterminal I38 is a terminal I59 communicating through line I60 with theterminal, I53. The solenoid I5I is adapted when energized to actuate theblades I6I, I62, I63 and the interlock or Ill adapted to be engaged bythe arm 30 so as to lift the push rod H3. 9

The press shown in Figure 1 furthermore comprises a conveyor II8 drivenby a motor II9 to carry the finished work away from the press, while afurther motor, generally designated I20, is provided for driving a pump.(not shown) used for circulating the coolant or cooling medium.

The specific wiring diagram as shown in Figure 9 shows two main linesystems of two different voltages of which the higher voltage mainsupply lines are used for operating the motors driving the main pumpswhereas the smaller voltage is used for operating the motors driving theconveyor and the pump used for circulating the cooling medium.

As will be seen from Figure 9, the solenoid 32 associated with the slowdownvalve 33 is connected on one hand with the terminal I2I and.

- The terminal I28 is also connected by line I3I with a terminal I32which, in its turn, is connected by line I33 with one end of thenormally open switch 3I which, as previously mentioned, is actuated .bythe press arm 30 for slowing down the movement of the press platenbefore contacting the work piece. The free end of the switch 3| when thelatter is in closed position contacts a terminal 300 connected by lineI34 with a terholding blade I64 so as to bridge their adjacentterminals. The terminal I53 furthermore communicates through 'line I65with the line I26 and through line I66 with one end of a resistance I61,the other end of which is connected with the filament of a bulb 299connected in its turn with the terminal I68. The terminal I68 isconnected by line I69 with a terminal I10 adapted to cooperate with aterminal HI and connected by line I12 with a terminal I13 cooperatingwith the terminal I14. A blade I15 is adapted selectively to bridge theterminals I13 and I14 when full automatic operation of the press isdesired or to bridge the terminals I10 and HI when semiautomaticoperation of the press is required.

The term full automatic operation means that the press performs aplurality of cycles without interruption, while the term semi-automaticoperation means that the press comes to a standstill after a completecycle. The terminal I14 is connected by line I16 with a terminal I11adapted to be engaged by one end of the normally open auxiliary startlimit switch I18 which is actuated at the retraction stroke of the pressplaten for I19 wit-h the'terminal I80 adapted to cooperate.

with the terminal I8I and connected by line I82 minal I35 and also withone end of a solenoid I36, the other end of which is connected by lineI31 with the terminal I38. The solenoid is adapted when energized toactuate the blades I46, I41 and I48 so as to cause the same to bridgetheir adjacent terminals. The switch 3| is also connected by line I39with the terminal I40 which normally engages the free end of thenormally closed position reversal switch "I which is actuated by thedownward press movement for causing the press to initiate its retractionstroke. The switch I H is connected by line I42 with the normally closedhigh pressure tonnage control valve 29, the free end of which when inclosed position engages the terminal I43 connected by line I44 with aterminal I45. Cooperating with the terminal I45 is a terminal I49.connected by line- I with one end of the solenoid I5I, the other end ofwhich isnonnected' by line I52 with a terminal I53. Cooperating with theterminal I53 is a terminal I54 connected with one end of with theterminal I49. The terminals I and II are adapted to be bridged by thepush button blade I 83 for causing forward movement of the press platenintended for hand starting.

The terminal I68 cooperates with the terminal I84 which is connected byline I85 with the terminal I86 normally connected with the terminal I81by the normally closed oil temperature limit switch I88. The switch I88is, actuated by a thermostat to break the circuit and stop automaticoperation when the oil temperature reaches a predetermined value. Theterminal I81 is connected-by line I51 with the terminal I 56. Theterminals I68 and I84 are adapted to be bridged by the reverse pushbutton blade I89 which is provided with a locking ring to make automaticoperation.

When hand operation is desired the switch I89 may be shifted so as toconnect the contacts I90 and I9I.

The main motor start button blade I92 is adapted to connect theterminals I93 and I94. The terminal I93 is connected by line I95 with aterminal I96 and by line I91 with a terminal I98 which latter is adaptedto be connected with the terminal I99 by the main inotor' stop buttonblade 200. lines- 20I and line 202 with the treminal 203 adapted to beconnected'with the terminal I96 by means of the interlock or holdingswitch blade 204. The terminal I99 communicates through line 205 withone end of a solenoid 206, the other end of which is connected by line201 with the line 208 leading on one hand to the terminal 209 I and onthe other hand to one end of a solenoid 2I0, the other end of whichisconnected by line 2 with the terminal 2I2. The terminal 209 isfurthermore connected by line 303 with the terminal 194. The terminal2l2is adapted to be The terminal I94. is connected by connected by theconveyor stop push button blade 2I3 with the terminal 2I4 connected byline 215 with the terminal m which latter is 3 adapted to be connectedwith the terminal 2I1 voltage supply by means of the conveyor start pushbutton blade 5 nnes 294 and 295/by lines 29s and 291.

Operation of first embodiment (Figures 1 to 9) In order to start theoperation or the press the switch blade I92 is actuated so as to connectinterlock or holding blade 204 to connect the 10 terminals I96 and 203with each other. Energization of the solenoid 220 furthermore causes theswitch blades 22I, 222 and 223 to connect the terminals 224, 225 and 226respectively with the terminals 221, 228 and 229. The terminals 221, 228and 229 lead to one of the motors for drivingone of the variabledelivery pumps. The terminals 224, 225 and 226 are respectivelyconnected bylines 230, 23I and 232 with the high voltage main supplylines lines 233, 234 and 235 are respectively connected with theterminals 236, 231 and 238 adapted,

when the solenoid 206 is energized, to be-connected with the terminals239, 240 and MI re- 233, 234 and 235. The

spectively leading to another motor for driving 25 the second variabledelivery pump. The connection of the said terminals is efiected in thisinstance by the blades 242, 243, and 244. The armature carrying theblades 242, 243 and 244 also carries an interlock-or holding switchblade 245 which, when the solenoid 206 is energized, connects theterminal 209 with the terminal 246 which in its turn is connected byline 241 with the terminal I93.

The solenoid 2I0 controls the operation of the switch blades 248, 249and 250 and 25I and also of the interlock or holding switch blade 252so, that energization of the solenoid 2I0 causes the said blades toconnect the terminals 253, 254, 255,

25s and 251 respectively with the terminals 258,

259, 260, 26I and 262. While the terminal 262 is connected by line 263with the terminal 2I6, the terminals 258, 259, 260 and 26I lead to themotor 1 I I9 for driving the conveyor H8.

The solenoid 264v controls the operation of the interlock or holdingswitch blade 265 and of the switch blades 266, 261, 268 and 269 in sucha manner that energization of the solenoid 264 causes the said bladesrespectively to connect the terminals 210, 21I, terminals 215, 216, 211,218 and 219. The terminals 216, 211, 218 and 219 leadto the motorI20 fordriving-the pump used for circulating the cooling medium. The terminal215 is connected by line 280 with'the terminal 28I turn is connected byline 282 with the terminal 283. The terminal 283 is normally connected'with the terminal 284 by the cooling pump switch blade 285 which whenbreaking the contact between the terminals cooling pump to stop. Theterminal 284 is con-' nected by line 286 with one end of the solenoid283 and 284 causes the said terminal '93, line 212, 213 and 214 with theWhlch in its in the followingma blade 204, terminal 203, line on onehand with the terminal 2" and on the,

other hand with the low voltage supply line I30. The terminal 212 isconnected ,with the low vdltage supply line I21 by line 289 on one handand onthe other hand by line 290 with the terminal 210 which in itstumis connected by line 29I with the terminal 292. The terminals 292 and28I may be bridgedhy the normally open cooling pump start switch blade293. The terminals 213 and 214 are respectively connected with the lowbridge their adjacent terminals. Closure of the switch blades I92, 2I8and 293 establishes the following circuits: r

From the low voltage supply line, I21 current flows through lines 289,290' and ,29l, the now closed switch blade 293, line 282, switch blade285 and line 286 to the solenoid 264 from which the current flowsthreugh line 281 to the low voltage main supp y line I30. In this waysolenoid 264 is energized and causes the closure of the blades 265, 266,261,268 and 269. The blade 265 establishes a holding circuit for thesolenoid 264 inasmuch as the current now flows from the line I30 throughlines 288, 281, the solenoid 264, line 286, blade 285, line 282,terminal 2 8I, line 280, blade 265 and lines 290 and 289 back to themain supply line I21. Consequently the blades 266, 261, 268 and 269remain in contact'with their adjacent terminals so that current flowsfrom the main supply lines I 30, I21, 294 and 295 respectively to thelines 288, 289, 296 and 291 and the blades 266, 261, 268 and 269 to theterminals 216, 211, 218 and'219 from where the current flows to themotor driving the cooling pump for the oil.

The closure'of the main motor start switch blade I92 causes the currentto flow from the low voltage main supply line I30 to the connectionpoint 30I and from there through lines 208 and 201 to the solenoids 220and 206 respectively, from where the current flows through the lines 2I9and 205 respectively to the terminal I99.

From here the current flows through the main' motor stop button blade200, line I91, now closed main motor start switch blade I92 andline 20Ito the junction point 302. ,From here the current flows through the line202 to terminal 255 222, 223 and 204 to bridge their adjacent terminals.Bridging of the terminals 246 and 209 by the holding blade 245establishesa holding circuit for-the solenoid 206, and bridging of theterminals 203 and I96 by the holding'blade 204 establishes a holdingcircuit for the solenoid 220 Current from the low voltage main supplyline I30 flows through the junction point 30I and the line 208 throughthe terminal 209 and from there throughthe blade 245, the terminal 246,line 241, terminal I96, holding 202, terminal 255 back to the mainsupply line I21. In case only one pump is to be driven so that thesolenoid 220 is not needed, the holding circuit for the solenoid 206will be established through the line 303 leading to the terminal I94.Since, due to the holding circuits the blades 242, 243 and 244 and alsothe blades 221, 228 and 229 are held in contact with their adjacentterminals, current will flow from the high voltage main lines 233, 234and 235 through the blades 242, the terminals 239, 240 and driving onepump, for through the lines 230, 23

24 I into one motor for instance pump l8 and I and 232 and the/blades243 and 244 and- I8I, terminal I55, solenoid 42, terminal I54, bladeI82, terminal I53 and lines I85, I28 back to the main supply line I21.The solenoid 42 actuates the control valve 33so as to lift the valvepiston 4|, thereby establishing communication between the conduit 38 andthe conduit 49.- Compressed air now flows through the line 35, thecontrol valve 39, the conduit 45 and the check valve 49a,

' from where it flows through the port 48 into the to the main supplyline I21. In this way solenoid' 2|0 is energized causing the blades 248,249, 250, 25I and 252 to bridge their-adjacent terminals. Bridging ofthe terminals 252 and 251 by the blade 252 establishes a holding circuitfor the solenoid 2|0 inasmuch as current now flows from the main supplyline I30, through connection point 30I, line 208, solenoid 2I0, line 2,switch blade 2I3, line 2|5, line 283, terminal 252, blade 252, terminal251, line 202, terminal 255 and from here back to the main supp y lineI21. The connection ofthe terminals 253, 254, 255 and 258 with theircorresponding terminals 258, 259, 280 and -28| by the blades 248, 249,250 and 25| enables current to flow from the main supply lines I30, I21,294 and 295 to terminals 258-, 259, 280 and 28l and from there to themotor 9 for driving the conveyor I I8. 4

Supposing a semi-automatic operation of the press is desired. To thisend the operator actucylinder bore 50 of the air cylinder 41. The airpressure acting on the piston 5| now moves the latter toward the rightwith respect to Figure 7. This movement is transferred to the shaft 82which, by means of the arm 1| keyed to the shaft 12, shifts the latterso as 'to actuate the rod or lever '18 and the arm 94 for moving thepumps its Figure 3 position by the platen arm '30, and

ates the switch blade I15 so as to cause the latter to connect theterminals I and HI with each other, while simultaneously the forwardpush button blade I83 is actuated to connect the terminals I80 and I8I.This simultaneous operation of the two blades I and I83 will force theoperator to use both hands, thereby causing him to withdraw his handsfrom the space below the press platen. Current will then flow from themain supply line I21 through lines I25 and I55 to the terminal I53 fromwhere it flows through the line I52, the solenoid I5I, line I50,terminal I49, line I82, the now closed switch blade I83, line 298,terminal "I, the now closed switch blade I15) terminal I10, line I59 toterminal I58. From here the current flows through the reverse pushbutton blade I89, line I85, the normally closed oil temperature limitswitch I88, line I51 and lines I58 and I29 to the main supply line I30.Simultaneously current flows from the supply line I21 through lines I28,I55 and I85, resistance I51, bulb 299 to the terminal I88 from where itreturns to the main supply line I30 through switch blade I89, line I85,blade I88 and lines I51; I58 and I29. The illumination of the bulb 299indicates in this way that the desired circuits are properlyestablished. Energization of the solenoid I5I causes the blades |8|,I52, I83 and the interlock or holding blade I84 to bridge their adjacentterminals so that a holding circuit for the solenoid I5I is establishedthrough the lines I30, I29, terminal I28, lines I3I, I33 and I39,position reversal switch |4|, line I42, the high pressure control valve29, line I44, the terminal I45, holding blade I54, terminal I49, lineI50, solenoid I5I, line I52, terminal I53, lines I85 and I25 to the mainsupply line I21. The blades I8I, I52 and I83 therefore remain in contactwith their adjacent terminals and establish circuits which will now bedescribed.

The blade I83 bridges the' terminals I59 and I38 while the blades I8Iand I82 respectively bridge the terminals I53, I54, I58 and I55. Conpushrod II3. Fluid pressure is now delivered by the pumps I8 and I9 throughconduits I1 and I8"into the upper portion of the press cylinder I3 sothat the press piston I4 and platen I5 move downwardly by gravity. Whilethis movement occurs, the push rod 3 due to the spring II5 follows thearm 30, and the arm I09 being free to move about shaft 12 follows thedownward movement of the push rod 3 so as to maintain its roundedportion III in contact with the collar 2 on the push rod II3. In thisway the jaw 0 moves from its Figure 4 position toward the position-shownin Figure 5. As soon as the press platen approaches the position whereit normally engages a work piece, the arm 30 actuates the switch 3"I soas to close the latter. Since, as mentioned above, due to theenergization of the solenoid I5I, the blade I53 had establishedcontactbetween the terminals I59 and I38, the closure of the switch 3|now causes current to flow from the low voltage main supply line I30through lines I29, I3| and I33 to the now closed switch 3| and fromthere through the solenoid I35, the line I31, the blade I83 and thelines I80, I85 and I25 back to the main supply line I21. Energization ofthe solenoid I38 causes the blades I48, I41 and I48 tobridge theiradjacent terminals. Connection between the tera holding circuit for thesolenoid I38 inasmuch as now the current flows from the. line I30through the lines I29 and I3I, the blade I43, the line I34, solenoidI38, line I31, blade I53 and lines'I50, I55 and I28 to the main supp yline I21. Bridging of the terminals I28-and I22 by the blade I41 and ofthe terminals I23 and I2'I by the blade I48 causes current to flow fromthe main supply line I39 through line I29, blade I41, solenoid 32, bladeI48, normally closed low pressure tonnage control valve 22 and line I28to the main supply line I21. In this way the solenoid 32 is energizedand causes an upward movement of the slow down piston 35 so thatcompressed air flows from the tank -31 through the line 35, the slowdown cylinder 33 and the line 45 from where it through the port 48 ofthe air cylinder 41. The compressed air entering through the port 48 nowacts upon the pis-.

ton area 304 of the piston 52 and inasmuch as the piston area 304 islarger than the piston area 305 of the piston 5| on which the compressedair admitted throughthe port 48 acts, the piston 52 moves toward theleft with regard to FIgure 7,;

thereby also moving the piston toward the left until the piston 52 abutsthe bottom portion 58- small choke openings 60, 65 and a throttlingaction is produced at the point of reversal of the reversible variabledelivery pumps so that a smooth initiation of'the retraction stroke isobtained. The shifting 'of the pumps into full stroke retractionposition causes a corresponding movement of shaft 12'due to the linkageIll, 16, so that the jaw I01 is moved into its Figure 6- position. Whenthe press platen .I5flnow cordance with the rate at which the pumpwithdraws fluid from the retraction side of the press piston I4.Although the platen arm 36, after a very short time, disengages theswitch-3I so that the latter is open again, this will not affect theslow down movement due to the fact that the solenoid I36 remainsenergized by the holding circuit through the blade I48. While the presspiston I4 moves downwardly by gravity, the surge valve 24' is opened,thereby admitting fluid from the fluid tank to the. upper portion of thepress cylinder I3 to supplement-the fluid delivered by the pump. Thedownward movement of the press piston I4 therefore continues withreduced speed until the platen I5 comes to a standstill by engaging thelower die unless a work piece was placed on the press bed and engaged bythe die connected to the platen. If during the downward movement of thepress piston I4 the die connected with the platen engages a work piece,pressure starts to build up in the upvalve 24 closes, whereas the lowpressure tonnage control valve 22 opens. Opening of the low pressuretonnage control valve 22 breaks the circuit through the solenoid 32 sothat the control 'valve piston 35 returns to its lowermost position,

thereby interrupting communication betweenthe air tank 31 and conduit 36on one hand and the conduit 45 on the other hand. Since furthermore nowthe conduit 45 is adapted to communicate with the bleeder opening 43,the pressure acting through conduit 49 upon the piston area 305 of thepiston 5I causes the piston 5I to move toward the right with respect toFigure '1 until piston 52, moved by the piston 5I, engages the cylinderhead 54. This movement is again transferred through the shaft 62 uponthe shaft 12 with the result that due to the linkage interconnecting theshaft 12 and the pumps I8 and I9, the pumps I8 and I9 are again moved tofull stroke delivery position. As a result thereof the downward movementof the press piston. I4 is speeded up and the actual pressing operationis effected with high speed. As soon as the pressing operationisfl'nished and a predetermined high pressure built up in the upperportion in the cylinder bore I3,.the. high tonnage control valve 29 isactuated by the-said high pressure so as to break the holding circuitforthe solenoid I5I. As a result thereof the blades I 6| and I62 return ttheir open position so that the solenoid 42 is deenergized and thecontrol valve piston 4| returns to its lowermost position. In thisposition the communication between the air tank 31 A per portion of thepress cylinder I3 and as soon as a minimum pressure is attained thesurge moves upwardly its arm 30 will, by engagement with'the collar II1,lift the push rod II 3 at the end of its retraction stroke so that thecollar H2, by engagement with the rounded portion III of the arm III9,.causes a shifting movement of the arm I09 and the shaft 12 so that thepumps I9 and I9 return 'to'substantially zero or nodelivery position,and the jaw I I0 moves from the position of Figure 6 intojthe positionof Figure 3. The press piston I4 therefore comes to a standstill and thepress is now ready for a new cycle. If, dueto leakage, the press pistonI4 should slightly move downwardly the. push rod II3 will likewise movedownwardly and so will the arm I99, thereby allowing, the springs 9I and9Ia to put the pumps again in retraction stroke position. The'piston I4will then be lifted to its previous position where the press again comesto a standstill.

If full automatic operation is desired, the blade I15 is actuated so asto connect-the terminals I13 and I14. The operation of the press willthen be carried out in the. same manner as previously described.However, in contradistinction to the semi-automatic operation, the

push rod II3 having adjustably mounted thereon a collar 306 moves theauxiliary start limit switch I18 so as to close the latter. Thisestablishes a circuit comprisingthe lines I30, I29, I58, I51 switchblade I88, line I85, blade I89, lines I69 and I12, blade I15, line I16,switch I13, line I82, line I50, solenoid I5I and lines I52, I65, I26 andthe main supply line I21. Consequently the solenoid I5I is energizedthereby causing the blades I64, I63, I62 and I6I again to bridge theiradjacent terminals in the manner previously described with the resultthat a new pressing cycle is started. By disconnecting the blade I15,the full automatic. operation may be ,inter rupted when desired. M W

automatic" operation the switch I18 will temporarily be closed, thiswill not'cause energization of the solenoid I5I since the blade I15 doesnot bridge the terminals I13 and'l14.

By disconnecting the blade 2I3 from the ,adjacent terminals 2 I2 and 2I4the circuit through the solenoid 2I0 is broken with the result that andthe conduit 49 is interrupted, while the connot opposed by air pressureacting on the pistons 5I and 52 so that the said springs will actuatetheir respective Shift rods 81 and I05 so as to move the pum s I8 and I9into full stroke retraction position. Due to the provision of the theconveyor motor ,I I9 comes to a standstill.

By disconnecting the switch .blade'285 from the terminals 283 and 284the circuit through the solenoid 264 is broken thereby interrupting thesupply of current to the cooling pump motor,

Similarly by disengaging the switch blade 200 from the terminals I93 andI99 the circuit comprising the solenoids 220 and 206 is broken therebyinterrupting the supply of current from the mainline 233, 234 and 235-tothe motors driving the va able delivery pumps I8 and I9. If neithersemiutomatic nor full automatic operation of thep ess is required andit, is merely desired tooperate the press by hand, for instance foradjusting purposes, the switch blade I89. is removed from its terminalsI68 and I84 and It will be noted that although at the semimoved tocontact .the dead; terminals I99 and some or Oasnarron To sum up theoperationdescribed above it may briefly be pointed out that after themotors ior the pumps I8 and i8 and the motors for the conveyor 8 and afurther motor for a pump der I3 and while the piston |4 moves downwardlyby gravity is supplemented by fluid from the a by the surge valve 24.Shortly before the ten l5 approaches its normal work piece en- I gosition, the platen arm 30 actuates the s tch 3| which is electricallyconnected with t e solenoid 32 so as to energize the latter, therebylifting the slow down piston 35 against the thrust of the spring 308 andestablishing communication between the conduit 35 and conduit 45. As aresult thereof compressed air from the tank 31 enters the air cylinder41 and moves the shaft 62 to such an extent that the latter causesmovement of the pumps l8 and I! to a materially restricted deliveryposition. The fluid expelled during this strokeof the piston in the aircylinder 41 passes through the conduit 48b, conduit 43, control valve 38into the conduit 38 and from there into the conduit 30. Since now only asmall quantity of fluid per stroke of the pumps l8 and I9 is withdrawnfrom the lower portion of the press cylinder l3, the press piston I4moves downwardly very slowly. This slow movement continues until thelower die is engaged unless a work piece placed-on the press bed engagesthe die connected to the platen l5. If this latter happens, a pressurestarts to. build up in the upper portion of the press cylinder I3 sothat the surge valve 24 closes. As soon as a minimum pressure isestablished in the upper portion of the ress cylinder i3, it actuatesthe low pressure tonnage control valve 22 so as to deenergize theSOlBIlLid 32. As a result thereof the spring 308 pushes the piston '35to its lowermost position. Compressed air ma then escape from theconduit 45 through the bleeder opening 43 while the compressed airpassing through the control valve 39 and the conduit 49 again shifts theshaft 82 toward the right, thereby again placing the pumps l8 and IS onfull stroke delivery position. The press now performs its pressingstroke at the end of which,- when a predetermined high pressure isobtained, the high pressure tonnage control valve 29 is actuated so asto break the 2,283,108 -While the press abovediscussed has beendescribed in connection with two pumps it is under stood of course thatthey may be replaced by a single pump without aflecting the operation ofthe press.

1 Second embodiment.

The press illustrated in Figure 10 corresponds in principle to the pressillustrated in Figures .1

to 9, and similar parts are therefore designated with the same referencecharacters. However,

, while the variable delivery pump I8 or is of the first embodiment isprovided with a spring illa and 3| respectively, continuously urging thepump into full delivery retraction stroke position, the variabledeliverypump 303 shown in Figure 10 is associated with two centeringsprings 3|0,

jacent the enlarged portion 3|8 is arranged a stop 3|3 continuouslyurged by a spring 3|! toward the push rod 3 but adapted by means of thesolenoid 320 to be moved away from the push rod 3 against the thrust ofthe spring 3|9.

The electric circuit for Figure 10, as far a it diflers from theelectric circuit shown in Figure circuit through the solenoid 42. Thespring 301 in the control valve 39 then pushes the valve piston 4|downwardly so as tointerrupt communi- V cation between the conduits 38and 48 while allowing the compressed air to escape from the conduits 48band 49 to the bleeder opening 44.

The springs 8| and 9|a of the pumps l9 and |8 now do not encounter anymaterial resistance so that they shift the pumps 8 and I3 to full delivery retraction position. The platen |5 now moves upwardly and at theend of its retraction stroke actuates, by means of the push rod 3,,

the arm I09 so as to cause the latter to move the pumps to neutralposition in case the press was adjusted for semi-automatic operation. Ifthe 9, is illustrated in Figure 11. The numeral 32| and 322 designatetwo main supply lines of which the line 32| is nnected by means of aline 323 with a terminal 324 adapted to be connected with a terminal 325by a starter switch 326. The terminal 325 is connected with one end ofthe sole- MM 321, the other end of which is connected by line 328 withthe other main sllpply line 322. The line 32| is furthermore connectedwith a terminal 328 normally connected with the ter-' minal 330 by thenormally closed emergency switch 33,|. The terminal 330 is connectedwith the normally closed high pressure tonnage control-valve 28 which inits closed position engages the terminal 332 connected with the terminal333 by line 334. The terminal 333 is adapted to be connected with theterminal 335 by means of the by means of the normally closed blade 345carried by the armature 348 cooperating with the solenoid 341. Theterminal 344 is connected by line 343 with the main supply line 322.Also connected with the armature 343 is the normally open blade 343which in its closed position connects the terminals 333 and 33| witheachother.

'The terminal 33| is connected by line 332 with the terminal 3l3normallyconnecte'd by means .oijthe normally closed tonnage'control valve 22with the terminal on which in its turn is connected by line 333 withfiiemain supply line 32|.

The terminalfll'is connectedby line 354 with the terminal 331 adapted-tobe connected with 1 the terminal 338 by means or the normally openswitch 31. The terminal363 is connected y line 360 with tlies lpp y line321. Connected with the junction point 361 in theline 366 is one end ofthe solenoid 341, the other end 'of which ply line 322. The junctionpoint 310 is furthermore connected with one end of the solenoid 320,

while the otherrend thereof is connected with the supply line 322. Theblade 363 is connected with an armature 311 cooperating with thesolenoid 312. One end of the solenoid 312 is connected by line 313 withthe supply line 322, whereas the other end of the solenoid 313 isconnected by line 314 with the'terminal 315 adapted to'be connected bymeans of the switch 359 with the terminal 3'16 which in its turn isconnected by line 311 with the main supply line Operation oj secondembodiment Suppose that the pump 303 is in its neutral position in whichthe armature 316 of the solenoid 312 is not impeded in its movement bythe stop 318. In order to start a working stroke of ,the press, thestarter switch 326 is actuated so.

as to connect the terminals 324 and 325 with each other. This causescurrent to flow from the supply line 321 through the line 323, the blade323, terminal 325, the solenoid 321 and the line 328 to the secondsupply line 322. Energize.-

broken, thereby de-energizing the solenoid 312,

while contact is established between the termihale-331 and 360 by meansof the blade 343. A holding circuit for the solenoid 341 isnowestablished through the lines 321 and 355, the low pressure tonnagecontrol valve 22-, line 352, blade 343, solenoid 341 and the line 322.De-energization of the solenoid 312 causes the centering spring3l0 tomove the armature 316 again to the right. However, when armature 316 wasmoved toward the left-the spring 313 had pushed forward the stop 318which-now prevents full return movement of the armature 316 so that thepump303 cannot return to zero position but re-. mains in restricteddelivery forward position. Consequently, the press piston 14 movesdownwardly with a materially reduced speed and continues this low speedmovement until the die carried by the platen engages the lower dieunless the die carried by the platen engages a work y piece placedon thepress bed. If this latter happens, pressure begins to build up in theupper portion of the cylinder bore 13 with the result that the surgevalve 24 closes. As soon as a predetermined minimum pressure has beenob-;' tained, the low pressure tonnage control valve 22 opens, therebybreaking the holding circuit for the solenoid 341. As-a result thereofthe armatture 346 moves downwardly to itsprevious positionso that-thecircuit through the solenoid 312 e is again closed. Re-energization ofthe solenoid tion of the solenoid 321 causes attraction of the armatureso that the blade 336 bridges the'terminals 333 and 335, therebyestablishing a holding circuit through line 321 with the normally closedemergency switch 331, high pressure tonnage control valve 23, line 334,blade 336, line 333, solenoid 321, line 328 and line 322. Although thestarter switch 326 will now return to open 312 causes the shift rod 314again to move toward the left against the thrust of the. spring 310,

thereby againplacing the pump into full stroke forward deliveryposition. The press now continues its pressing stroke until apredetermined high pressure is obtained which actuates the high pressuretonnage control valve 23 so as to. cause the latter to disengage theterminal 332,

thereby breaking the holding circuit for the solenoid 321. As a resultthereof the armature 331 returns to its lowermost position in which theblades 336 and 342 disengage their adjacent terminals, while theblade,362 bridges the terminals 363 and 363. Consequently, current nowflows from the main supply line 321 through the line position, thearmature 331, due to the just men- I tioned holding circuit, remainsattracted. Therefore, blade 342 bridges the terminals 340 and 341 sothat current flows from the line 321, through the line 333, blade 342,the solenoid 312, the

7 closed blade 3'45 and the line 348 to the main supply line 322. On theother hand, the blade 362 will disengage the terminals 363 and 364.Energization of the solenoid 312 moves the shift rod 314 and therebytheflow control member toward theleft against the thrust of the spring 310so as to move the pump 303 into full delivery forward-position. Nowpressure fluid is delivered by the P111111 303 through line 318a intothe upper portion of the'press cylinder 13, while the fluid expelledfrom the lower portion of the press cylinder 13 may escape through theline 318 to the suction side of the pump. As soon as the press piston 14approaches its normal work piece engaging position, the press arm 30actu- 365,-the blade 362, line 366, blade 368, through both thesolenoids 310 and 320 to the main supplylin 322. In this way thesolenoids 310 and 320 are energized with the result that the stop '313is withdrawn, while the armature 311 is moved against the thrust of thespring 311 toward the right so as to place the pump 303 on full strokeretraction position. The pumpnow delivers pressure fluid through line313 into the lower portion of thecylinder. bore 13, while the fluidexpelled from the upper portion of the press cylinderbore 13 may esc pethrough the line 31611. When the platen 15 reaches the end of itsretraction stroke the pla n arm" 30 actuates the switch 353 so as tothereby causing current .to flow from thesupply line 321 through theline 311, switch 353, line 314, solenoid 3'12 and line 313 to the supplyline 322. .Energizatlon'ol the solenoid 3'12 causes a lifting movementof the armature 311 with the blade 368-, thereby breaking the circuitcomprising the solenoids 313 and 320. Since the solenoid 312 waspreviously de-energized, the centernow elosed switch 31, the line 356and the solenoid 341 to the other supply line 322. As a reing spring 311now moves the shift rod 315 toward the left so as to move the'pump 303to neutral or no delivery position. The device is now ready for a newcycle. It will be-noted that the movement of the shift rods 313 and 314by the spring 311 is not impeded by the stop 316- ose the latter,

since the latter merely engages the longitudinal wall portion of thearmature 3l3. j

Third embodiment and cooperating with a solenoid 333 .in such a.

manner that energization of the solenoid 333 actuates the shift rod 333so as to cause the pump to move to full stroke delivery position.

The armature 33! and thereby the shift rod 333 is continuously urgedtoward the left side with respect to Figure 12 by spring 333 so as tomove the pump 313 to restricted delivery position. A stop 333 preventsthe shift rod 333 from moving the pump to zero or'neutral position. Thesuction side of the pump 313 is connected by means of the conduit 335with the fluid tank 33, while the pressure side of the pump 313communicates through a conduit 333 with a fourway valve 331. Thefour-way valve 331 does not form a part of the present invention and maybe of the. type described in detail in U. 8. Patent No. 2,190,939 toErnst. The four-way valve 331 has a connection 333 witl'ithe fluid tank33 and two further connections 333, 333 respectively, leading to theupper and lower portion of the press cylinder bore I33. The four-wayvalve 331 is controllable by a valve rod 33I having at its lower end acollar 333 adjustably mounted thereon. which is adapted to be engaged bythe platen arm 33 when the platen approaches the end of its retractionstroke. The upper portion of the valve rod 33! is provided with anarmature 333 which is continuously urged downwardly by a spring 333 butadapted by ene tion of the solenoid 335 to be lifted against th thrustof the spring 333. As in the previously described device, the upperportion of connected with a line .33I leading to a terminal .333 adaptedto be connected with aterminal 333 by means of the switch blade 333carried by the armature 335. The terminal 333 is connected withConnected with the main supply line as is a' line 333 which is connectedwith one end of the solenoid 335 and also with one end of the solenoid333. The other end of the solenoid 335 is connected with a line 3! 3adapted to be connected with a line 3 leading to line 331 by means ofthe press cylinder bore l3 communicates with a conduit 13 which in itsturn communicates with a low pressure tonnage control valve 33 and ahigh pressure tonnagecontrol valve 33 in the Asimplifled wiring diagramfor Figure 12 is shown in Figure 13. According to this embodiment lines333 and 331 constitute the main supply lines. The supply line 333 isconnected with a line 333 which in its turn is connected with oneterminal of the normally open high pressure ton-- nage control valve 33.The other terminal pertaining to the high pressure tonnage control valvea switch blade 333 carried by the armature 335. The other end of thesolenoid 333 is connected with a line 3! 3 adapted to be-connected witha line 3 leading to line 331 by means of a switch blade 3 carried by thearmature 3 I 5. The armature 5 also carries a switch blade 3 adapted toconnect the lines 3" and 3!3,with each other. The line 3 i1 is adaptedto be connected with the line 3 leading to line 333 by means of the lowpressure tonnage control valve 33. The line 313 is connected to one endof the solenoid 333 which cooperates with the armature 5 and the otherend of which isconnected by a line 33! with the main supply line 331.The line 3" is connected at its junction point with the solenoid 333with a line 433 adapted to be connected by means of the platen operableswitch 3! with the line 333 leading to the supply line 333.

Operation of third embodiment conduits 333 and 333, while energizationof thesolenoid 333 causes actuation of the shift rod 333 so as to movethe pump 3" to full'stroke delivery position. Pressure fluid is nowsupplied by the pump 313 through conduits 333 and 333 to the upperportion of the press cylinder bore. I

I3 which fluid is supplemented by fluid from the tank 33 through thesurge valve 33. The press piston 33 now carries out a quick downwardmovement by gravity. As soon as the press platen l5 approaches itsnormal work piece enga ing position, the platen arm 33 closes the switch,3! thereby enabling current to flow from the line 333 through line 333,switch 3|, line 333, solenoid 333, line 33! to the supply line 331. Inthis way the solenoid 333 is energized thereby causing a lifting.movement of the blades H3 and 3 so that the blade 3! 3 connects the line'3" with the line 3", thereby establishing a holding circuit for thesolenoid 333, while a lifting movement of the switch blade 3 breaks theconnection between the 1ines'3!3 and 3 !1 so as tone-energize thesolenoid 333. As soon as the solenoid 333 is de-energized, the spring333 '33 is connected by line 333 with one end of a solenoid 333, theother end of which is connected with the main supply line 331, The line333 is at its junction point with the solenoid 333 also pulls thearmature 33! over toward the left until it engages the stop 333. Thismovement ofthe armature '3" is conveyed through the shift rod 333 to thepump 313 so as to move the latter to a restricted delivery position.Consequently only a small quantity of fluid is delivered by the pump 313to the upper portion "of the press cylinder bore IS with the result thatthe advance movement of the press piston l4 ismaterially slowed down.The press piston now continues its downwardmovement with the thusreduced 'speed until it encounter resistance offered by a work piece. Ifthis occurs pressure builds up in the upper portion of the presscylinder l3 thereby -closing the surge valve 24, and when apredetermined minimum pressure in the upper por- 3. Consequently,current from the supply line 390 -again flows to line 409 and fromthere, in the previously described manner, through the solenoid 382 sothat energization thereof causes the pump 319 again to move to fullstroke de-.

livery position. The advance movement of the press platen is thereforeagain speeded up and the actual pressing operation is now effected. Assoon as at theend of the pressing operation a predetermined highpressure is obtained, this pressure actuates the high pressure tonnagecontrol valve 29 in such amanner as to cause the latter to establishconnection between the lines 398 and 399. Current now flows from thesupply line 396, through line 398, the high pressure tonnage controlvalve 29, line 399 and solenoid 400 to the supply line 391. In this waythe solenoid 400 is energized which causes the armature 405 to moveupwardly so that the b1ade 404 connects the terminals 402 and 403 witheach other, 1 while the blade 424 breaks the connection between thelines 410 and 4. The blade 404 thus establishes a holding circuit forthe solenoid 400 which comprises the main supply line 390, normallyclosed emergency switch 401, line 406, blade 404, line 40l, solenoid 400and main supply line 391. Interruption of the connection between thelines 4 and M0, due to the lifting movement of the blade 424, causesde-energiz'ation of the solenoid 395 so that the spring 394 -moves thevalve rod 391 downwardly, thereby establishing connection between theconduits "386 and 390, while breaking connection between the conduits386 and 389. Consequently pressure fluid is now delivered by the pump319 through conduits 38B and 390 to the lower portion of the presscylinder bore I3, thereby efiecting the retraction of the press pistonI4. When the press platen approaches the end of its retraction stroke,the platen arm 30 engages the collar 392 so as to lift the valve rod39l, thereby shifting the four-way valve 381 to neutral position inwhich the delivery of the pump 319 is by-passed through line 388 to thetank 23. The press iston I4 thereby comes to a standstill, in which/ itremains until a new cycle is started.

.If, due. to leakage between the upper portion and the lower'portion ofthe press cylinder I3, the press piston l4 should slightly movedownwardly, the valve rod 39l with its collar 392 will, due to thespring 394, follow the platen arm 30, .thereby again establishingconnection between the conduit 386 and the conduit 390 so that thepiston I4 is moved upwardly again until it has reached the end of itsretraction stroke as previously described.

It is understood that we desire to comprehend within our invention suchmodifications as come within the scope of theclaims.

Having thus fully described our invention what we claim as new anddesire to secure by Letters Patent, is:

1. In a hydraulic press, a press cylinder, a press ram reciprocablymounted in said press cylinder, a fluid source adapted to supplypressure fluid to said press cylinder for actuating said ram, controlmeans associated with said fluid.

source for varyingthe delivery oi fluid thereof to said press cylinderand for changing the direction of flow of said fluid to said presscylinder, slow down means operable to actuate said control means forslowing down the movement of said ram prior to resistance being exertedupon said ram by a work piece to be pressed, and means responsive to aresistance exerted by a work piece upon said ram for actuating saidcontrol means so asagain to speed up the advancing movement of said ram.

2. In a hydraulic press, a press cylinder, a press ram reciprocablymounted in saidpress cylinder, pumping means adapted to supply pressurefluid to said press cylinder for actuating said ram, control meansassociated with said pumping means for varying the delivery of fluidthereof to said press cylinder and for changing the direction of flow ofsaid fluid tosaid press cylinder, means responsivev to a predeterminedposition of said pressram for actuating said control means to slow downthe advancing movement of said ram, and means responsive to a presurefluid tov said press cylinder for actuatingsaid press ram, control meansassociated with said fluid source for varying the delivery of said fluidsource to said press cylinder and the direction of flow from said fluidsource to said .press cylinder, means operatively connected to' saidcontrol means and responsive to a predetermined position of the ram forcausing a reduction in the delivery of said fluid source to initiateaslow down action upon the press ram during its advancing stroke, andfluid means adapted in response to a predetermined pressure on said ramto actuate said control means for increasing" the delivery of said fluidsource, thereby. causing said rain to again speed up after saidslow downoperation.

4. In a hydraulic press, a press cylinder, a press ram reciprocablymounted in said press cylinder, a variable delivery pump adapted tosupply'pressure' fluid. to said press cylinder for actuating said pressfram, means for initially placing said pump into full delivery position,control means operatively connected with said 0 variable delivery'pumpfor restricting the pumping stroke thereof in response to apredetermined position of saidpress ram, and restoring means operativelyconnected with said pump and stricting means for causing said pump toresume its full delivery stroke.

6. In a hydraulic press, a press cylinder, a press ram reciprocablymounted in said press cylinder, a fluid source adapted to supplypressure fluid to said press cylinder for operating said press ram,means for initially placing said fluid 2,2as,1 os

1y connected with said valve means and responsive to a predeterminedpressure on said ram for conveying pressure from said pressure supplymeans to said cylinder-piston-assembly for causing the latter to restoresaid pump to full delivery position.

9. In a hydraulic press, a hydraulically operable press-ram, a variabledelivery pump for supplying pressure fluid to said press ram, an airpressure operable cylinder-piston-assembly connected with said pump forvarying the flow of fluid thereof, air pressure supply means to supplycompressed air to said cylinder-piston-assembly, means for'causingcompressed air from said air pressure supply means to actuate saidcylinder-piston-assemblfi so as to put the pump on full delivery stroke,ineans responsive to the source into increased delivery position,controlmeans including pressure operable means operatively connectedwith said fluid source for restricting the delivery of said fluid sourcein response to a predetermined position of said ram, and meansoperatively connected with said pressure operable means for restoringthe initial delivery of said fluid source in response to a predeterminedresistance encountered by said press ram.

'7. In a hydraulic press, a press cylinder, 9. press ram reciprocablymounted in said press cylinder, a reversible variable delivery pumpadapted to supply pressure fluid to said press cylinder for actuatingsaid press ram, means for initially placing said pump into full deliveryforward stroke position, pressure supply means, a pressure operablecylinder-piston-assembly, valve means controlling the supply'of pressurefrom said pressure supply means to said pressure operablecylinder-'piston-assembly, means operatively connecting said pressurecylinder-piston-assembly and said variable delivery pump for varying thedelivery of fluid and the direction of the flow of fluid of said pump,means responsive to a predetermined position of said press ram forcontrolling said valve means so as to cause said pressurecylinder-piston-assembly to shift said variable delivery pump to arestricted delivery position, and means responsive to a predeterminedpressure in said press cylinder and adapted to operate said valve meansso as to cause said cylinder-piston-assembly to restore said variabledelivery pump to full delivery forward stroke position.

said pump for varying the flow of fluid thereof,

valve means interposed between said cylinderpiston-assembly and saidpressure supply means for controlling the conveyance of pressure fromthe latter to said cylinder-piston-assembly, starter means forcontrolling said valve means to admit pressure from said pressure supplymeans to said cylinde'r-piston-assembly to cause the latter to move thepump to full delivery position, means responsive to the movement'of saidpress ram and adapted to control said valve means so as to causepressure from said pressure supply mean actuate saidcylinder-piston-assembly for red cing the delivery stroke of saidadvancing movement of said press mm for controlling the supply ofcompressed air, ,to said cylinder-piston-assembly so as to reduce thedelivery stroke of said pump, means responsive to a predetermined lowpressure in said press cylinder for controlling the supply of compressedair to said cylinder-piston-assembly so as to restore said pump to fulldelivery position, and means responsive to a predetermined high pressurein said press cylinder for reversing the direction of flow of pressurefluid from said pump to said press ram.

10. In a hydraulic press, a hydraulically operable press ram, areversible variable delivery pump for supplying pressure fluid to saidram, means for initially putting said pump on an increased deliverystroke, pressure fluid supply means, a link including a differentialcylinderpiston-assembly adapted to be supplied with pressure fluid from,said pressure supply means, a linkage interconnecting said link withsaid pump for varying the delivery stroke thereof and the direction ofthe flow of fluid from said pump, a follower operatively connected withsaid linkage and adapted to effect a' shifting 'movement of said pump toneutral position, a push rod adapted to engage said follower foractuating the same, means'for allowingsaid follower to continuouslyengage saidpush rod, said push rod being operable in response .to apredetermined positionof said ram, slow down means operatively connectedwith said link for restricting the delivery stroke of said pump inresponse to a predetermined position of said ram, means responsive to apredetermined low pressure on said ram for causing said link to restoresaid increased delivery stroke of said pump for the rest of theadvancing movement of 'said ram, and means responsive to a high'pressureon said ram for causing said link to reverse the delivery of said pump.

11. A hydraulic press comprising in combination a hydraulically operablepress ram, a oneway variable delivery pump for supplyingi'pressure fluidto said ram, means forinitially placing said pump into full strokedelivery position,

' valve means associated with said pump for varying the direction offlow of pressure fluid to saidram, means for reducing the deliverystroke of said pump in response to a predetermined position of said ramduring its advancing stroke, and means responsive to a' predeterminedpressure on said ram for restoring said pump to its full de liverystroke for the rest of the advancing movement of said ram.

12. A hydraulic press comprising in combinationa press ram, 'a one-wayvariable delivery pump for supplying. pressure fluid to said ram,

pump, and pressure responsive means operativemeans for initially placingsaid pum into full aaaaies to full delivery position.

13. A hydraulic press comprising in combination a hydraulically operablepress ram, a one way variable delivery pump for supplying pressure fluidto saidpress ram, means for initially placing said pump into full strokedelivery position, valve means associated with said pump for controllingthe direction of flow of pressure fluid to said ram, electriccontrolling means responsive to a predetermined position of said pressram for reducing the delivery stroke of said pump, means responsive to apredetermined low pressure on said ram during the advancing strokethereof for restoring said pump to full delivery stroke position, andmeans responsive to a high pressure acting on said press ram at the endof its advancing stroke for causing said valve means to reverse thedirection of flow of pressure fluid from said pump to said ram.

14. In a hydraulic press, a one-way variable delivery pump, meansassociated with said pump for urging said pump to neutral or no-deliveryposition, stop means for preventing said pump from reaching neutral orzero position, a hydraue lically operable press ram adapted to besupplied with pressure fluid from said pump, means for initially placingsaid pump .into full delivery po-' sition, means responsive to apredetermined position of said ram for reducing the delivery stroke ofsaid pump, means responsive to a predetermined pressure on said ram forreturning said pump to full delivery position, valve means adaptedselectively to vary the direction of flow of pressure fluid from saidpump to said ram or to by-pass the delivery of said pump to ex-' haust,means responsive to a pressure higher than said first mentioned pressurefor actuating said valve means to reverse the direction of flow ofpressure fluid from said pump to said ram,

and means responsive to a predetermined position on the retractionstroke of said ram for causing said valve to by-pass the delivery ofsaid pump to exhaust.

15. A hydraulic press comprising in combinafluid source in response to apredetermined position of said ram during its advancingstroke, and meansresponsive to a predetermined presreturning said, pump to full strokeposition. v

said pump into full delivery forward stroke position, means responsiveto a predeterminedadvancing position of said press ram forde-energizingsaid electric means to allow movement of said pump to areduced delivery position,. means for preventing said pump from moving:

to zero position during its advancing stroke, and

means responsive to a prede rmined pressure during the advancing strokeof said ram for 17. In a hydraulic press, .a press mm, a reversiblevariable delivery pump for supplying pressure fluid to said ram toactuate the same, yielding means for continuously urging said pumpto'zero or no-delivery'positiomelectric means adapted to oppose saidmeans for selectively moving said pump to full stroke forward orretraction position, means responsive to a predetermined position .ofsaid ram during its advancing stroke for de-energizing said electricmeans, to allow said yielding means to effect a sure on said ram forrestoring said increased delivery of said fluid source for the rest ofthe advancing stroke of said ram.

16. In a hydraulic press, a reversible variable delivery pump, a pressram operable by pressure reduction in the delivery of said pump, stopmeans operable during said delivery reducing operation by said yieldingmeans for maintaining said pump in a reduced delivery position, andmeans responsive to a predetermined pressure on said ram during itsadvancing stroke for re-energizing said electric means to cause the pumpto resume its full stroke forward position.

18. In a hydraulic press, a press ram, a reversible variable deliverypump for supplying pressure fluid to said press ram, means associatedwith said pump for continuously urging said pump toward neutralor-no-delivery position, electric means adapted to cause movement ofsaid pump to full delivery position, stop means operableto preventmovement of said pump from full stroke forward position tolneutralposition, means responsive to a predetermined position of the ram duringits advancing stroke for deenergizing said electric means whileoperating said stop means to allow said pump to return to a restricteddelivery forward position, and means responsive to a predeterminedpressure on said ram during its advancing stroke for re-energizing saidelectric means to return said pump to full stroke forward deliveryposition.

19. In a hydraulic press, a press ram, a reversible variable deliverypump for supplying pressure fluid to said press ram, means associatedwith said, pump for continuously urging said pump toward neutral orno-delivery position, electric means adapted to cause movement of saidpump to full delivery position, stop means operable to prevent movementof said pump from full stroke forward position to neutral position,-

means responsive to a predetermined position of the ram during'itsadvancing stroke for deenergizing said electric means while operatingsaid stop means to allow said pump to return to a restricted deliveryforward position, means responsive to a predetermined pressure at theendof the advancing stroke of said ram for withdrawing'said stop meansand causing said electric means tomove said pump to full strokeretraction position, and means operative ata predetermined position onthe retractionstroke of said-ram for de-energizing said electric meansto allow return of said pump to no delivery position.

20. In a hydraulic press, a press rani, a re versible variable deliverypump for supplying to the initiation of a working cycle for actuatingpressure fluid to said press ram, spring means delivery forward vassociated with said pump for continuously urging the lattertowardneutral or no delivery position, shifting means operable to oppose saidspring means selectively to move said pump to full stroke forward orfull stroke retraction posi:

'tion, means response to a predetermined posi-- tion of the ram duringits advancing stroke to allow movement of said pump to a reduced forwardstroke position, means responsive to a predetermined low pressure onsaid ram for actuating saidshifting means to move 'said pump to fullstroke forward position, and means responsive to a predetermined highpressure on said ram for actuating said shifting means so as to shiftthe pump from full stroke forward position to full stroke retractionposition.

7 21. In a hydraulic press, a press ram, a reversible variable deliverypump for supplying pressure fluid to said ram, spring means on oppositesides of said pump adapted to move said pump to neutral or no-deliveryposition, firstelectric means operable to shift said pump to full strokeforward position, second electric means operable to shift said pump tofull stroke retraction position, stop means operable to maintain saidpump on a reduced forward stroke, starter means for energizing saidfirst electric means to move said pump to full stroke forward position,switch means responsive to a predetermined position of said ram tode-energize said first electric means and to make said stop meanseflective, means responsive to a predetermined pressure acting on saidpress ram for re-energizing said first electric means, means adapted tode-energize said first electric means and energize said second electricmeans at the end of the 6 versible variable delivery pump for supplyingpressure fluid to said ram, spring means on opposite sides of said pumpadapted to move said pump to neutral or no-delivery position, firstelectric means operable to shift said pump to 10 full stroke forwardposition, second electric means to move said pump to full stroke forwardposition, switch means responsive to a predetermined position of saidram to de-energize said first electric means and to allow said stopmeans to maintain said pump on said reduced forward stroke, meansresponsive to a predetermined pressure acting on said press ram forre-ener- I gizing said first electric means, means responsive to apressure higher than the last mentioned pressure acting on said ram atthe end of its advancing stroke for de-energizing said first electricmeans and energizingsaid second electric means, means operableconcomitantly with the energization of said second electric means forwithdrawing said stop means from its stopping position, and meansresponsive to a predetermined position on the retraction stroke of saidram for de-energizing said second electric means to allow said pump toreturn neutral position.

WALTER ERNST.

PHILIP J. LINDNER.

